试述微管的化学组成、类型和功能。

A How to Use a Painting Knife 使用画刀的方法
Painting with a knife is a bit like putting butter on bread and produces quite a (1) result to a brush. Painting knives are excellent for producing textured, impasto work and (2) areas of flat colour.
What’s the difference between a palette knife and a painting knife
A palette knife is a long, straight spatula that is used (3) mixing paints and scraping a palette clean. They’re made from metal, plastic, or wood and (4) either be completely straight or have a slightly bent handle. A painting knife has (5) large crank in the handle, which takes your hand away from the painting surface. They (6) in numerous shapes(for example pear-, diamond-, or trowel-shaped) and are used for painting (7) of a brush. The edge of the knife is blunt, so that it doesn’t cut the (8) .
·What shape of painting knife should I use
Different shaped painting knives produce different effects. For example, a short blade produces angular strokes (9)a long blade makes it easy to put down sweeps of colour.
·Why can’t I use a palette knife to paint with
You can. Painting (10) just have the advantage of coming in more angular shapes and with sharper points. And (11) larger crank in the handle means there’s less chance of rubbing your knuckles into wet (12) . If you’re unsure whether you’re going to enjoy painting with a knife, first buy a (13) , plastic palette knife and experiment a bit with this before upgrading to a wood-and-metal knife.
·How do I use painting knife
(14) the handle firmly so you’re got good control. Pick up some paint off your palette (15) the tip, as you’d pick up some butter with a knife. Use the side of the (16) to spread paint across your canvas, or press it onto the canvas, as you (17) spread butter across a slice of bread．It’ll seem strange at first as it’s quite (18) to using a brush. Using just the tip of the blade will produce small dots. (19) the edge of the knife down will produce fine lines. Pressing the blade flat down (20) the paint will produce ridges. Scrape back into the paint to reveal underlying layers (called sgraffito).

在垂直除尘风管上装设插板阀、插板应从上向下插倾斜（）。

A.30°

B.45°

C.60°

D.70°

能够表明水资源在经济与社会发展中的重要程度的特性是水的（）。

A.不可替代性

B.多功能性

C.有限性

D.区域性

李白《古风》第三首：“秦王扫六合，虎视何雄哉！挥剑决浮云，诸侯尽西来。明断自天启，大略驾群才。收兵铸金人，函谷正东开。……刑徒七十万，起土骊山隈。尚采不死药，茫然使心哀。……但见九泉下，金棺葬寒灰。”这首诗（）。

A.全诗都批评秦王不施仁义

B.全诗都总结了秦亡的教训

C.前半部歌颂秦王一统天下，后半部批评他

D.前半部谴责秦王使用暴力，后半部指责他

经济合同争议申请仲载的期限为多少？